﻿<p>
 The schema <em>IfcMaterialResource</em> contains the types and entities that are used to define materials (substances,
 of which products are made of). Materials are defined generically.
</p>
<blockquote class="note">
 NOTE&nbsp; The references to the usage of materials is made from the relevant elements through the objectified
 relationship <em>IfcRelAssociatesMaterial</em>.
</blockquote>
<p>
 Material definitions are distinguished by how they apply to elements or element types and by their components (layers,
 profiles, parts).
</p>
<p>
 Material designation can be made for standard element occurrences to support a limited range of their parametric representation using
</p>
<ol>
 <li>a structured set of material layers <em>IfcMaterialLayerSetUsage</em> and how the layers relate to the reference axis or plane,</li>
 <li>a structured set of material profiles <em>IfcMaterialProfileSetUsage</em> and how the profiles relate to the reference axis.</li>
</ol>
<blockquote class="note">NOTE&nbsp; 
 Often specific subtypes of building elements are used to have such parametric representations associated, they use the 
 common suffix 'StandardCase', for example <em>IfcWallStandardCase</em>, or <em>IfcBeamStandardCase</em>.</blockquote>
<p>
 Material designation can be made for element occurrences or element types without applying a parametric meaning using
</p>
<ol>
 <li>a set of material layers (with a specified configuration by sequence and thickness of material layers)
  <em>IfcMaterialLayerSet</em>, or </li>
 <li>a set of material profiles (with a specified configuration by positioning and outline profile of material
  profiles) <em>IfcMaterialProfileSet</em>, or</li>
 <li>a set of materials (without a specified configuration or structure) <em>IfcMaterialConstituentSet</em>, or</li>
 <li>as fallback by a single material <em>IfcMaterial</em> (including composite materials),</li>
</ol>
<p>
 These options are exposed for association with <em>IfcElement</em> or <em>IfcElementType</em> and their subtypes
 through a select type <em>IfcMaterialSelect</em>. The association is realized by the objectified relationship
 <em>IfcRelAssociatesMaterial</em>, accessible by the inverse relationship <em>AssociatedTo</em>. Some associations to
 specific material entities may be restricted as not being appropriate within the specialized element or element type definitions.
</p>
<p>
  The following material properties and information sets can be assigned to an <em>IfcMaterialDefinition</em>, or only to a
  single <em>IfcMaterial</em>.
</p>
<ul>
 <li>Material properties;</li>
 <li>Material classification and material library reference;</li>
 <li>Material presentation in shape models (e.g. by color, hatching, rendering);</li>
 <li>Relation to the ingredients of a material composite.</li>
</ul>
<blockquote class="history">
 HISTORY&nbsp; New schema in IFC1.0
</blockquote>
<blockquote class="change-ifc2x4">
 IFC4 CHANGE&nbsp; Definition of material properties and their assignment to <em>IfcMaterial</em> or other appropriate
 options in <em>IfcMaterialSelect</em> is now fully captured by <em>IfcExtendedMaterialProperties</em> using the general
 <em>IfcProperty</em> approach. Specific predefined subtypes of <em>IfcMaterialProperties</em> are no longer available.
</blockquote>
<blockquote class="deprecated">
 DEPRECATION&nbsp; Material designation by using <em>IfcMaterialList</em> is deprecated and should not be used.
 The classification of materials should not be done using <em>IfcMaterialClassificationRelationship</em> anymore (entity
 type deprecated); the <em>IfcExternalReferenceRelationship</em> in <em>IfcExternalReferenceResource</em> schema should be used
 instead.
</blockquote>